Overhead electric transmission line



F. M. CRAP@ OVERHEAD ELECTRIC TRANSMISSION LINE Filed May 23, 1955 May17, 1938.

Patented May 17, 10:',a- 02,118,008,

UNITED STATES PATENT OFFICE.l

OVERHEAD ELECTRIC TRANSMISSION LINE Frederick M. Crapo, Muncie, Ind.,assignor to Q Indiana Steel & Wire Company, Muncie, Ind.,

a corporation of Indiana Application May 23, 1935, Serial No. 23,009

10 Claims. (Cl. 173-13) My invention relates to overhead electrictransrous conductor, the area in solid-line crossmission lines usingferrous conductors, with parhatching indicating the preferred area, andthe ticular reference to a--c.- transmission lines alarea in broken-linecross-hatching indicating a -though my invention is not limited to a-c.lines. permissive area. v

My invention is applicable for instance, for pow- Heretofore the ferrousconductors in general er lines, telephone lines, telegraph lines, signaluse for telephone, telegraph, and signal lines, and lines, etc., and isof especial value for telephone in some instances for power lines, havebeen of transmission lines; and the conductors involved three generalcommercial grades known as E. B.- may be not only the Wires of thetransmission cir- B. (Extra Best Best), B. B. (Best Best), `and cuitproper, but also include various ancillary Steel, Approximate tensilestrengths and d-c. 10

conductors, such as ground Wires, shield wires, resistivties of thesegrades are as follows:

messenger cables, catenary supports, etc., which 1 may be primarily forother than conducting pur- Approximate I Approximate poses and/or mayactually serve to conduct cur- Grade @mrgsislliy gnsilungth l5 rent onlyoccasionally. Therefore, by the term no pofd e sfaremcger 15 overheadelectric transmission line, I mean an overhead line which may berequired to carry electric current; and by the terms ferrous congj Bductor or "carbon-steel conductor I mean a St -0750 551000 conductorwhich may be required to serve as a 20 current-carrier for an electricalsystem and of f Three other commercial grades of ferrous conwhich thecross-section is mainly of ferrous maductors have also been used in someinstances terial, specifically carbon steel in my invention, for powerlines; especially for overhead ground and any coating (as of zinc orcopper) is a relawires and/or shield wires, and for long spans suchtivelysmall part of the cross-section. The term as wide river crossings.These other three grades 25 carbon steel is used in its accepted sense,(as` are commonly known as lSiemens-Martin, shown by The Making,Shaping, and Treating High strength", and Extra-high strength, and ofSteel, by Camp and Francis, published by the ,are named in the order ofincreasing tensile Carnegie Steel Company, Fourth Edition, pagesstrengths and d-c. resistivity. Approximate 259 and 707, generallyaccepted as authorltative,) tensile strengths and d-c. resistivities ofthese 30 as meaning steels in which carbon is the element three gradesare as follows: fundamentally Vemployed to control physical properties'and in which the manganese is 1es s in Approximate Approximate amountthan about 1.0%, although 1n previous Grade Ad-- resistivity tensileStrength hypo-eutectoid carbon steels it has usually been m0 llfml e.msilrgxsic er 35 greater in amount than the carbon. It is the obJect ofmy .mventlon to produce a siemensMamn 7280 00' 000 transmission line ofcarbon-steel conductor (un- High strength 8320 140,000 coated or coatedas with zinc or copper) which Exim-002111800118@ 9300 200,000

40 has its tensile strength and its electrical con- 40 ductivity bothrelatively high. Generally inthe In all the grades known asSiemens-Martin", prior art an increase in tensile strength in ferrousHigh strength",` and Extra-high strength", the conductors has beenobtained at the cost of deadvantages of increased tensile strength havecreased electrical conductivity, and an increase in been obtained at thesacrifice of electrical conelectrical conductivity at the cost ofdecreased ductivity; so that while the tensile strengths of 45 tensilestrength; but by my invention I am able such grades are substantiallygreater than those to get both relatively high. of E. B. B., B. B., orSteel, above men- The accompanying drawing illustrates my irltioned,their electrical conductivities are subvention: InA such drawing, Fig. 1is a diagram- 'stantiallyless Such increased tensile strengths maticview of an overhead electric'transmission .have been obtainedfundamentally by making the 50 line, of ferrous conductor, in accordancewith my wires of steels'which have high contents of Acarinvention,` theparticular character" of ferrous bon, and/or to some extent and in somecases conductor being indicated by a legend on the by heat treatmentand/or by cold-working the drawing; andFig. 2 is a diagram showing thematerial in the process of wire drawing.

contents of carbon and manganese in such fer- In the carbon-steelconductors -of the prior art 55 of overhead electric transmission,however, the carbon content and the manganese content and the relationbetween them have been such that when an increase in tensile strengthhas been obtained it has been at the cost of a decrease in electricalconductivity; Generally speaking, increases in tensile strength havebeen obtained 4by increasing both the carbon content and the manganesecontent, with the manganese content generally materially exceeding thecarbon content until the carbon rises well. above 0.25%; for manganeseis qualitatively like carbon in that an increase in it tends to;increase the tensile strength.

Both an increase in carbon and an increase in manganese, however, notonly tend to increase tensile strength but also tend to increase d-c.

resistivity. But the effects of increases in carbon and manganese,respectively, diiier as between themselves in their eects dn tensilestrength and on electrical conductivity; for the addition of carbon tocarbon steel increases tensile strength in proportionately greaterdegree but increases d-c. resistivity in proportionately less degreethan does the addition of an equal amount of manganese, and, conversely,the elimination of managnese decreases tensile strength inproportionately less degree but decreases d-c. resistivity inproportionately greater degree than does the elimination of an equalamount of carbon.l

Heretofore high manganese has in general been assumed to be necessary inany mediumcarbon and higher-carbon steels Iused in transmission lines,for various reasons and especially for cleansing the steel in theprocess of manufacture; and its effect in increasing the 'd-c.resistivity, if considered at all, either was deemed not seriouslyobjectionableor was considered unavoidable. Y

I have done some previous work, partly in connection with Frank F.Fowle, in overcoming the diillculties of the general prior art referredto above; and either alone or jointlyv with him have illed certainpatent applications relating thereto, as follows:

A. In the Crapo Patent No. 1,942,441, granted January 9, 1934, there isdescribed -a carbonsteel conductor in which the carbon content is .notless than 0.25%.

B. In the co-pending Fowle & Crapo application, Serial No. 705,830,filed January 8, 1934, now Patent No. 2,019,447, granted October 29,1935, there is described a carbon-steel conductor in which the carboncontent is not less than 0.25%, and the manganese content is not inexcess of 0.30%.

C. In the co-pending Crapo application, Serial No. 705,831, led January8, 1934, now Patent No. 2,019,445, grantedoctober 29, 1935, there isdescribed av carbon-steel conductor in which the carbon content is lessthan 0.50%, the manganese content is less than 0.30% when the carboncontent exceeds 0.25%, and the carbon steel has the characteristicswhich are produced by quenching from above a critical temperature by aliquid medium having a temperature below the melting point of lead.

According to my present invention, the carshall be not in excess of thecarbon content, and

e templates that there shall be at least some cold working either beforeor after the application of any protective metallic coating, and thateffects of cold working shall persist in the iinal conductor.

The cold working may if desired be preceded by any desired annealing,either partial or complete, or by other desired heat treatment. Indeed,it is sometimes advantageous, especially when relatively'high tensilestrength is desired, to subject' the conductor to patent-annealing priorto the final cold working; in which case the conductor will haveproperties characteristic of those produced by that combination oftreatments.

It is not prohibitive to do some partial annealing after cold working;such as the partial annealing which incidentally occurs when a harddrawnferrous conductor is passed through a bath ofl molten zinc in thehot-dip process of galvanizing. It is sometimes desirable to avoid eventhat partial annealing; in which case any metallic protective coatingwhich is applied after the nal cold working may be applied byelectrodeposition.

`My present invention is thus concerned fundamentally with th carboncontent and the manganese content, and the production of characteristicsdue to cold working, in the general class of carbon steels. Variousother elements which may exist in carbon steels, such as silicon andphosphorous and sulphur, may also be present in varying small amounts;and the carbon steels may be copper-bearing steels. The phosl phorousdesirably does not exceed 0.04% if the conductor is to be coated byelectro-deposition, and 0.08% if it is to be coated by hot-dipping aswith zinc; .the sulphur desirably does notv exceed 0.05%; and thesilicon desirably does not exceed 0.025% unless a zinc coating is to beapplied by hot-dipping, and even then desirably should not exceed 0.12%.Even with hot-dipping. it is desirable that only phosphorous, or onlysilicon, but not both, exceed the lower limit given. Copper, if present,as to improve corrosion resistance, may be Yof the usual amountemployed, commonly not over 0.30%.v

Thus my transmission line comprises a carbon-steel conductor (coated ornot) which has carbon and manganese contents and cold-workedcharacteristics as defined above.

Such a transmission line has the advantage of relatively hifh electricalconductivity, for both direct currents and alternating currents, ascompared with previous ferrous transmission lines of correspondingcarbon contents. It is especially advantageous for alternating orpulsating currents, because of the decreased magnetic permeabilityandthe consequent `decreased skin effect due to the carbon and to thecoldworking, and to the patenteannealing ifv used. AAt the same time, byhaving the carbon and manganese contents in the range noted, and by thelcold working, and by the patent-annealing if used, I get high tensilestrength. Thus Iy combine high tensile strength with high electricalconductivity.

The followingtwo examples are illustrative of my invention: Y

a. An example of carbon-steel conductor used in my' invention is a No.12 B. W. G. galvanized steel wire in which the steel containedapproximately 0.21% of carbon, and approximately 0.17% of manganese; andin which the silicon was 0.014%, the phosphorous 0.014%, the sulphur0.030%, and the copper 0.24%. This wire has been cold-drawn in the-customary manner, and was then so galvanized By the hot-dip processthat its temperature was not raised sufficiently high to eliminate theeffects produced by the cold-drawing.

b. Another sample of this wire was processed in the same way, exceptthat it was patent-annealed before cold-drawing.

The following table shows the properties of the two samples justdiscussed, in contrast to those of an example of commercial B. B.telephone wire of the same No. 12 B. W. G. size:

I claim as my invention:

1. An overhead electric transmission line, comprising a conductor whichis to carry current, and which is of carbon steel which has beencold-worked andI in which substantial effects characteristic of thoseproduced by such coldworking persist; and of which the carbon content isless than 0.25% but not less than 0.12%, and the manganese content isnot in excess of 11A; times the carbon content and in any case is not inexcess of 0.30%.

2. An overhead electric transmission line, comprising a conductor whichis to carry current, and which is of carbon steel which has beencold-worked and in which substantial eiects characteristic of thoseproduced by such coldworking persist; and of which the carbon content isless than 0.25% but not less than 0.12%, and the manganese content isnot in excess of 11A, times the carbon content and in any case is not inexcess of 0.30%, and the sum of the carbon content and manganese contentis not over 0.40%.

3. An overhead electric transmission line, com- Tensile D-c. re-Etective Skim Ratio of tenstrength: sistance: a-c. resisteffect silcstrength in pounds in olli lnce: in resistance to eilectlivte per squareper o ms per a-c. res s inch met 100e feet m0 am Example oi commercialB. B. telephone wire. v57, 500 6. 35 9. 97 1. 670 5, 767

Exemples l telephone wires oi this application:

non-patented before cold drawing 101, 200 6. 8. 94 l. 394 ll, 320 (b)Patented before cold drawing 114,000 6. 8.93 1.386 12,770

The three wires compared are all galvanized wires. The a-c. currentsused had a frequency of 1000 cycles per second, and a strength of 5milliamperes. I took a frequency `-of 1000 cycles per second as a fairsingle-equivalent voice frequency; and I took a current of 5milliamperes as being within the ordinary range of telephonietransmission currents.

Although the d-c. resistances of the wires embodying the presentinvention are very closely similar tothe dc. resistance of the "B. B.telephone wire, yet the effective a-c. resistances of lthe wires of thepresent invention are materially lower than the a-c. resistance of theB. B. telephone wire, and the tensile strengths of the wires of thepresent invention are almost double the tensile strength of the B. B.telephone wire; so that the ratio of tensile strength to effective ar-o.resistance is about twice as great as thatrratio for the B. B."telephone wire.

By building an overhead transmission line of a carbon-steel conductor(coated or uncoated) conforming to the above requirements, it ispossible to have both high tensile strength and high electricalconductivity. Such a transmission line is of value for both alternatingand direct currents, and for the transmission of electric power as wellas of telephone, signal, and telegraph currents.

It is also advantageous for ground wires, shield wires, messengercables, catenary supports, etc.; and either as a single wire or in astranded cable. But it is of special advantage for the transmission ofrelatively high-frequency currents, such as those used in telephonietransmission; where the frequency is voice frequency, of the order of100 to 3000 cycles per second, and the currents are usually small, notexceeding about 50 milliamperes.

prising a conductor which is to carry current, and which is of carbonsteel which has been coldworked and in which substantial eifectscharacteristic of those produced by such cold-working persist; and ofwhich the carbon content is less than 0.25% but not less than 0.12%, andthe manganese content is not in excess of the4 carbon content.

4. An overhead electric transmission line, comprising a conductor whichis to carry current. and which is of carbon steel which has beencold-worked and in which substantial effects characteristic of thoseproduced by such coldworking persist; and of which the carbon content isless than 0.25% but not less than 0.12%. andthe manganese content is notin excess of the carbon content, and the sum of the carbon content andmanganese content is not over 0.40%.

5. An overhead electric transmission line, com-V prising a conductorwhich is to carry current, and which is of carbon steel which has beencold-worked and in which substantial effects characteristic of thoseproduced by such coldworking persist; and of which the carbon content isless than 0.25% but-not less than 0.15%, and the manganese content isnot in excess of 11/3 times the carbon content andin any case is not inexcess of 0.30%.

6. An overhead electric transmission line, comprising a conductor whichis to carry current, and which is of carbon steel which has beencold-worked and in which substantial effects characteristic of thoseproduced by such coldworking persist; and of which the carbon content isless than 0.25% but not less than 0.15%, and the manganese content isnot in excess of 1% times the carbon content andin any case is not inexcess of 0.30%, and the sum of the carbon content and manganese contentis not over 0.40%.

7. An overhead electric transmission line, com prising a conductor whichis to carry current, and which is of carbon steel which has beencold-worked and Ain which substantial eiccts characteristic of thoseproduced by such coldworking persist; and of which the carbon content islessthan 0.25% but not less than 0.15%, and the manganese content is notin excess of the -carbon content.

8. An overhead electric transmission line, comprising a conductor whichis to carry current, and. which is of carbon steel which has beencold-worked and in which substantial effects characteristic of thoseproduced by such cold- 15 working persist; and oi which the carbon con--tent is less than 0.25% but not less than 0.15%, and the manganesecontent is not in excess of the carbon content, and thesum of the carboncontent and manganese content is not over 9. An overhead electrictransmission line, comprising a conductor which is to carry current, andwhich is of carbon steel which been cold-worked and uin whichsubstantial. effects characteristic of'those produced by suchcoldworking persist; and of which the carbon content is less than 0.25%but not less thanv 0.12%, and the manganese content-is not in excess of1% times thevcarb'on content and in anycase is notin excessof 0.30%;.and which has been patent-annealed prior' to the cold-working.

10. An overhead electric transmission line. comprising a conductor whichis to carry current, :and which is of carbon steel which has .beencold-worked andin' which substantial efi'ects characteristic of thoseproduced bysuch cold-'working persist; and of which the carbon contentis less than 0.25% but not less than 0.15%, and the manganese content isnot in excess ci' 1%, times the carbon content and in any case is not inexcess of 0.30%; and which has been patent-snnealed'prior to thecold-working. 20

FREDERICK u.

